EP3569466B1 - Sensor for detecting metal parts and method for reducing a magnetic field - Google Patents

Description

The present invention relates to a sensor for detecting metal parts, in particular metallic or partially metallic wheels of a rail vehicle, a use of at least two such sensors and a method for attenuating a magnetic field emanating from a rail vehicle.

In general, devices for detecting metal parts, especially for detecting metallic or partially metallic wheels on rail vehicles, are implemented using inductive sensors. This requires a high level of safety, despite only sporadic use. An example of such an application area is rail transport. The following refers to the use of such sensors or such a method in rail transport. However, this does not imply any restriction to this application area.

In the field of railway transport, it is common for a sensor to detect metal parts, in particular metallic or partially metallic wheels of a rail vehicle, to be arranged parallel in the longitudinal direction of the rail, i.e. parallel to the direction of movement of the wheels of the rail vehicle. Such a sensor provides signals with high availability, which are usually routed via a cable to an indoor system and processed accordingly. This enables functions such as the presence detection of a rail vehicle, the direction of travel detection or a track vacancy detection in the form of an axle count to be implemented. This is used, for example, in EN 36 32 316 A1 shown.

It is also common for each sensor to consist of a sensor coil and an oscillator circuit. The sensor coil forms an oscillating circuit with a capacitor and creates an alternating magnetic field in its surroundings. A metal part of a railway wheel that penetrates the effective range of the sensor coil dampens the oscillating circuit because the iron of the railway wheel draws energy from it through eddy current losses. This results in the voltage amplitude or the voltage frequency of the oscillating circuit changing, which is converted into a change in the current consumption of the sensor. This measurement signal is fed via a two-wire line into the internal system of a security system and processed there or prepared for processing.

The mounting position of the sensor is predetermined within narrow limits by the geometry of the rail or by the railway wheel. Irrespective of this, however, a problem arises that the rail vehicle can also emit magnetic fields with such a high intensity that a voltage is induced in the sensor coil. This process can lead to a state in the electronics that incorrectly transmits the presence of a wheel to the higher-level evaluation electronics. There, this leads to incorrect information that can disrupt the operation of the railway network. Such magnetic fields emitted by the rail vehicle are generated, for example, by eddy current brakes, magnetic rail brakes or a high current consumption by the drive units of the rail vehicles.

For example, the prior art document DE 199 15 597 A1 an arrangement of a figure-of-eight coil that is aligned in the direction of travel of the rail vehicle. The two partial coils of the figure-of-eight coil are connected in such a way that a magnetic field that is emitted from a distance significantly greater than the extent of the figure-of-eight coil is already compensated in the figure-of-eight coil.

The state of the art document DE 101 37 519 A1 attempts to solve the problem described above by an additional coil, which is embedded in the actual transmitting or receiving coil.

The WO 2010/052081 A1 describes an arrangement in which one coil is the transmitting or receiving coil and a second coil serves exclusively for compensation. This second coil is arranged at least one third of the coil diameter of the transmitting or receiving coil below.

The EN 10 2009 053 257 A1 discloses an arrangement of sensor and compensation coil with a total of three coils.

However, various disadvantages have arisen in the prior art. For example, the magnetic field emitted by the rail vehicle either hits the sensor coil at different times, or a compensation arrangement for an induced voltage is very difficult to implement. One disadvantage is the arrangement of a figure-of-eight coil in the direction of movement of the rail vehicle. This means that first one partial coil of the figure-of-eight coil, then both partial coils of the figure-of-eight coil, and at the end of the sensor coil's passage only the last partial coil of the figure-of-eight coil is flooded with the disturbing magnetic field of the rail vehicle. However, a figure-of-eight coil is only effective if it is flooded at the same time with approximately the same intensity. For this reason, an interference voltage is induced, particularly when only one partial coil of the figure-of-eight coil is flooded, as occurs at the beginning and end of the passage of the wheel of the rail vehicle.

Generally speaking, when a wheel of a rail vehicle passes over the sensor coil, the outer coil and then the middle coil are affected by the magnetic field first. Only when both coils are flooded with the magnetic field emitted by the rail vehicle does optimal compensation occur. Another disadvantage of the state of the art is that compensation coils are usually mounted below the actual transmitting or receiving coils, which means that the compensation coils do not experience the same intensity of the magnetic field emitted by the rail vehicle as the transmitting or receiving coils. The reason for this is that the magnetic field becomes weaker as the distance from the source increases. This ensures complete compensation. prevented and an interference voltage remains. A further disadvantage is the very complex coil constructions that require too much space, particularly for the railway sector. The complicated coil constructions also have the disadvantage described above that the coil is not exposed to the same magnetic field at every point in time when a wheel of a rail vehicle passes over it.

It is therefore an object of the present invention to eliminate or at least minimize the disadvantages known from the prior art.

This object is achieved according to the invention by a sensor according to claim 1.

The term "approximately at an orthogonal angle" is understood to mean in particular an arrangement of the sensor coil at an angle of 70° to 110° to a direction of movement of the metallic or partially metallic wheels of the rail vehicle, whereby this arrangement is related to the longitudinal axis of the sensor coil. Preferably, this arrangement is at an angle of 80° to 100°, particularly preferably 85° to 95°. It is also possible that this is an orthogonal angle in the mathematical sense, i.e. a right-angled (90°) angle.

The sensor according to the invention offers the advantage that the magnetic field emitted by a rail vehicle is weakened. This prevents the induction of a voltage which is induced in the sensor coil by such a magnetic field. This is achieved by the sensor coil, which is designed as an air coil, being arranged approximately at an orthogonal angle to the direction of movement of the metallic or partially metallic wheels of the Rail vehicle. As a result, the magnetic fields emanating from the rail vehicle are weakened at the moment they reach the sensor coil due to the coil structure and the coil positioning. The structure of the sensor coil, in particular the windings which are not electrically conductively connected at a crossing point, also ensures that only the magnetic fields emanating from the rail vehicle are compensated. The magnetic field generated by the sensor coil, which is influenced by the metallic or partially metallic wheels and is used by the sensor to detect the presence of the wheel of a rail vehicle, is not impaired by the object according to the invention. In particular, the present invention is based on the finding that the magnetic fields emitted by the rail vehicle have, to a good approximation, the same direction and similar intensities at every point of rail contact. The generators of this magnetic field emitted by the rail vehicle are located at a distance from the sensor coil which is large compared to the dimensions of the sensor coil. This is used both in the construction, especially in the windings, and in the approximately orthogonal positioning of the sensor coil, which ensures the compensation of the voltage induced by the magnetic field emitted by the rail vehicle.

Preferably, the windings are arranged in a circle. This makes it easier to produce the sensor coil and provides a known shape.

It has also proven to be advantageous that the windings of the sensor coil are arranged in the shape of a figure eight along the longitudinal axis. This allows the detection direction of the sensor coil to be precisely configured. With such a shape, it is also possible to focus the detection cone of the sensor coil, which means that the metallic or partially metallic wheels of a rail vehicle to be detected can be detected at a greater distance from the sensor coil.

From a functional point of view, it has proven to be advantageous that the windings, due to their circular arrangement in the longitudinal axis of the sensor coil, define two coil parts that are connected in series. One advantage of this is that a coil structure known in the prior art can be used. can be achieved, thereby achieving the advantages of this coil structure known in the prior art.

In a further embodiment, when current flows through the two coil parts, one coil part has a magnetic north pole and the second coil part has a magnetic south pole. This ensures that at all times, including when a wheel of a rail vehicle is passing over, the magnetic fields emitted by the rail vehicle strike the two coil parts of the sensor coil at the same time. This induces a voltage in the two coil parts, which, however, cancel each other out due to different signs.

Advantageously, the windings of the sensor coil lie in a plane whose surface normal is approximately parallel to the metallic or partially metallic wheels of the rail vehicle. In a further embodiment, the windings of the sensor coil lie in a plane whose surface normal forms an acute angle with the metallic or partially metallic wheels of the rail vehicle. Such arrangements allow the excitation direction of the sensor coil to be set precisely.

Preferably, the product of the area of the first coil part multiplied by the number of turns of the first coil part is equal to the product of the area of the second coil part multiplied by the number of turns of the second coil part. This creates a sensor coil that is symmetrical with respect to its longitudinal axis, with two symmetrical areas and the same number of turns. Such a sensor coil is particularly advantageous when the magnetic fields emitted by the rail vehicle impinge symmetrically on the sensor coil. This makes it possible to weaken an induced voltage that occurs due to the symmetrically emitted magnetic fields.

It has also proven to be advantageous if the windings span asymmetrical areas. From a functional point of view, it has proven to be advantageous if the product of the area of the first coil part multiplied by the number of turns of the first coil part is not equal to the product of the area of the second coil part multiplied by the number of turns of the second coil part. This is particularly advantageous if the magnetic fields emitted by the rail vehicle are applied asymmetrically to the sensor coil. This can further reduce any induced voltage that occurs due to the asymmetrical emitted magnetic fields. Since the magnetic fields emitted by the rail vehicle are stronger near a rail head, the emitted magnetic field is often asymmetrical and therefore also often hits the sensor coil asymmetrically. It can happen that a residual voltage can be measured on the sensor coil even after compensation, which can continue to disrupt the electronics in their function. Because the windings have different numbers of turns and span asymmetrical surfaces, the residual voltage can be reduced to a minimum, or reduced to zero, so as not to impair the detection of metal parts, especially metallic or partially metallic wheels of a rail vehicle.

The object set out at the beginning is also achieved by using at least two sensors according to one of the preceding embodiments for determining a direction of movement of a rail vehicle. This achieves the advantages of the sensor.

The object is also achieved according to the invention by a method according to claim 7.

The advantages of the sensor are achieved by the method according to the invention.

In addition, by mounting the sensor coil at an approximately orthogonal angle to a direction of movement of the metallic or partially metallic wheels of the rail vehicle, a weakening of a magnetic field emanating from a rail vehicle is achieved, largely independent of the local conditions.

With regard to the advantageous embodiments of the method listed in the claims, reference is made to the advantages described with reference to the advantageous embodiments of the sensor. These advantages are also achieved by the respective embodiments of the method.

Figur 1

eine schematische Darstellung einer ersten Ausführungsform der erfindungsgemäßen Sensorspule in Form einer Luftspule;

Figur 2

eine zweite Ausführungsform der Sensorspule;

Figur 3

eine dritte Ausführungsform der Sensorspule.

Further details and advantages of the invention will now be explained in more detail with reference to some preferred embodiments shown in the drawings. They show:

Figure 1

a schematic representation of a first embodiment of the sensor coil according to the invention in the form of an air coil;

Figure 2

a second embodiment of the sensor coil;

Figure 3

a third embodiment of the sensor coil.

In particular, it should be noted that the sensor coil of the present invention is designed in such a way that the magnetic fields emitted by the rail vehicle, as a result of the coil structure and the position of the sensor coil, generate a voltage in the sensor coil that compensates for itself the moment they reach the sensor coil. The structure and positioning of the sensor coil thus ensure that only the externally interfering magnetic fields compensate for themselves. The desired magnetic field, i.e. the magnetic field that is used to detect metal parts, in particular metallic or partially metallic wheels of a rail vehicle, is not impaired by this structure and positioning.

The Figure 1 shows a schematic representation of a first embodiment of the sensor coil 1 according to the invention in the form of an air coil. The dashed arrow 5 indicates a direction of movement of a wheel of a rail vehicle (not shown). The sensor coil 1 shown has a longitudinal axis 3 and two windings 2, 2', which intersect in an electrically non-conductive manner at a crossing point 4. Each of the windings 2, 2' defines a coil part 7, 7', with a first coil part 7 having an area A ₁ and a number of windings n ₁ . Analogously, a second coil part 7' has an area A ₂ and a number of windings n ₂ . The current flow is also shown schematically which flows through the two coil parts 7, 7'. The sensor coil 1 is located at an approximately orthogonal angle to the rail heads 9, 9'. A magnetic field of the rail vehicle, which is emitted by it, is not shown. Even without the magnetic field being shown, it is clear that the magnetic field of the rail vehicle enters the coil parts 7, 7', or the windings 2, 2' of the sensor coil 1, and is weakened both by the symmetrical design of the sensor coil 1, and by the approximately orthogonal positioning of the sensor coil 1, or the voltage induced by this magnetic field in the respective coil parts 7, 7' is compensated. The electronics connected to the sensor coil 1 (not shown) are therefore not affected by any interference voltage.

In the Figure 2 a sensor coil 1 according to a second embodiment is shown schematically. The windings 2, 2' of the sensor coil 1 have the shape of a cornered figure eight, whereby they intersect in an electrically non-conductive manner at an intersection point 4. The direction of movement 5 of a wheel 8 of a rail vehicle is also shown schematically. The windings 2, 2' are located in a plane which is spanned by the first rail head 9 and a second rail head opposite it (not shown). The sensor coil 1 is located at an approximately orthogonal angle to the direction of movement 5 of the wheels of the rail vehicle. The surface normal of the plane spanned by the windings 2, 2' is approximately parallel to the metallic or partially metallic wheels 8 of the rail vehicle. Also shown schematically is a magnetic field 6 of the rail vehicle which is emitted by it. This magnetic field 6 can be generated, for example, by an eddy current brake, by magnetic rail brakes or by a strong current consumption by the drive units of the rail vehicle. The magnetic field 6 of the rail vehicle enters the coil parts 7, 7', or the windings 2, 2' of the sensor coil 1, and is attenuated by both the symmetrical design of the sensor coil 1 and the approximately orthogonal positioning of the sensor coil 1. In other words, the voltage induced by this magnetic field 6 in the respective coil parts 7, 7' is compensated. The electronics connected to the sensor coil 1 (not shown) are therefore not affected by any interference voltage.

The Figure 3 shows a sensor coil 1 according to a third embodiment. The windings 2, 2' of the sensor coil 1 have the shape of a cornered figure eight, and they intersect in an electrically non-conductive manner at a crossing point 4. In contrast to the previous embodiments, the surface normal of the plane spanned by the windings 2, 2' describes an acute angle with the metallic or partially metallic wheels 8 of the rail vehicle. The sensor coil 1 is located at an approximately orthogonal angle to the direction of movement 5 of the wheels of the rail vehicle. A magnetic field 6 of the rail vehicle is shown schematically, which is emitted by it. The magnetic field 6 of the rail vehicle enters the coil part 7, or the winding 2 of the sensor coil 1, with a higher intensity than in the coil part 7', or the winding 2'. In order to nevertheless enable a weakening of the emitted magnetic field 6, or the voltage induced by it, the winding 2' has a different area A ₂ , which is larger in the present embodiment, and also a different number of turns n ₂ than the winding 2, or its area A ₁ , or number of turns n ₁ . Both the different areas A ₁ , A ₂ , and the different numbers of turns n ₁ , n ₂ result in a magnetic field 6 of the same size in relation to the magnetic flux in each of the limbs of the coil parts 7, 7'. Consequently, a voltage of the same magnitude is induced. This ensures that the emitted magnetic field 6 is weakened, or the voltage generated by this field in the two coil parts 7, 7' is of the same magnitude, which means that no interference voltage occurs in any electronics connected to the sensor coil. This is achieved both by the orthogonal arrangement to the direction of movement 5 of the wheel of the rail vehicle 8, as well as by the shape of the sensor coil 1 and by the different surfaces or numbers of turns.

List of reference symbols

1

Sensor coil

2, 2`

Winding

3

Longitudinal axis

4

Crossing point

5

Direction of movement of the wheels of a rail vehicle

6

magnetic field of the rail vehicle

7, 7'

Coil part

8th

Wheel of the rail vehicle

9, 9'

Rail head

Claims (12)

1. A sensor for detecting metal parts, particularly metallic or semi-metallic wheels of a rail vehicle, comprising an electrical resonant circuit having at least one sensor capacitance and one sensor coil (1) which generates a magnetic field, whereby same is an air-core coil,
   characterized in that

   the windings (2) of the sensor coil (1) are arranged relative their longitudinal axis (3) such that a crossover point (4) of the windings (2) results, wherein the windings (2) define two coil sections (7, 7') connected in series due to their circular arrangement in the longitudinal axis (3) of the sensor coil (1), and/or wherein as current flows through the two coil sections (7, 7'), one coil section (7) spans a magnetic north pole and the second coil section (7') spans a magnetic south pole,

   wherein relative to its longitudinal axis (3), the sensor coil (1) is arranged at an angle in the range of between 70° and 110° to a direction of movement (5) of the metal parts of the rail vehicle, wherein voltages induced in the respective coil sections (7,7') cancel each other out due to different signs.
2. The sensor according to claim 1,
   characterized in that
   the windings (2) are arranged circularly.
3. The sensor according to claim 1 or 2,
   characterized in that
   in the longitudinal axis (3), the windings (2) of the sensor coil (1) are arranged in a figure-eight.
4. The sensor according to one of the preceding claims,
   characterized in that
   the windings (2) of the sensor coil (1) lie in a plane, the surface normal of which is approximately parallel to the metallic or semi-metallic wheels (8) of the rail vehicle.
5. The sensor according to one of claims 1 to 3,
   characterized in that
   the windings (2) of the sensor coil (1) lie in a plane, the surface normal of which forms an acute angle with the metallic or semi-metallic wheels (8) of the rail vehicle, and/or wherein the product of the area (A₁ ) of the first coil section (7) multiplied by the number (n₁ ) of windings of the first coil section (7) equals the product of the area (A₂ ) of the second coil section (7') multiplied by the number (n₂ ) of windings of the second coil section (7').
6. The sensor according to one of claims 1 to 3,
   characterized in that

   the windings (2, 2') span asymmetrical areas (A₁, A₂ ), and/or

   wherein

   the product of the area (A₁ ) of the first coil section (7) multiplied by the number (n₁ ) of windings of the first coil section (7) does not equal the product of the area (A₂ ) of the second coil section (7') multiplied by the number (n₂ ) of windings of the second coil section (7').
7. A method for weakening a magnetic field (6) originating from a rail vehicle comprising the step: installing a sensor coil (1) of an electrical resonant circuit, wherein the sensor coil (1) is an air-core coil,
   characterized in that

   the windings (2) of the sensor coil (1) are arranged relative their longitudinal axis (3) such that a crossover point (4) of the windings (2) results, wherein two coil sections (7, 7') connected in series are defined by the circular arrangement of the windings (2, 2') in the longitudinal axis (3), and/or wherein as current flows through the two coil sections (7, 7'), the first coil section (7) spans a magnetic north pole and the second coil section (7') spans a magnetic south pole,

   wherein relative to its longitudinal axis (3), the sensor coil (1) is arranged at an angle in the range of between 70° and 110° to a direction of movement of the metal parts of the rail vehicle, wherein voltages induced in the respective coil sections (7,7') cancel each other out due to different signs.
8. The method according to claim 7,
   characterized in that
   the windings (2, 2') are arranged circularly.
9. The method according to claim 7 or 8,
   characterized in that
   in the longitudinal axis (3), the windings (2, 2') of the sensor coil (1) are arranged in a figure-eight.
10. The method according to one of claims 7 to 9,
    characterized in that
    the windings (2, 2') of the sensor coil (1) are arranged in a plane, the surface normal of which is approximately parallel to the metallic or semi-metallic wheels (8) of the rail vehicle.
11. The method according to one of claims 7 to 9,
    characterized in that

    the windings (2, 2') of the sensor coil (1) are arranged in a plane, the surface normal of which forms an acute angle with the metallic or semi-metallic wheels (8) of the rail vehicle, and/or

    wherein

    the product of the area (A₁ ) of the first coil section (7) multiplied by the number (n₁ ) of windings of the first coil section (7) equals the product of the area (A₂ ) of the second coil section (7') multiplied by the number (n₂ ) of windings of the second coil section (7').
12. The method according to one of claims 7 to 10,
    characterized in that

    asymmetrical areas (A₁, A₂ ) are spanned by the windings (2, 2'), and/or wherein

    the product of the area (A₁ ) of the first coil section (7) multiplied by the number (n₁ ) of windings of the first coil section (7) does not equal the product of the area (A₂ ) of the second coil section (7') multiplied by the number (n₂ ) of windings of the second coil section (7').

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